1. Field of the Invention
The present invention relates to a striking tool which performs various operations such as chipping, crushing of a member to be scraped such as concrete.
2. Description of the Related Art
A striking tool has been known which is driven by a motor and arranged to perform the various operations such as chipping, crushing of a member to be scraped such as concrete. An example of such a striking tool is shown in FIGS. 6 and 7.
That is, FIG. 6 is a perspective view showing the external appearance of a conventional striking tool 101 and FIG. 7 is a partially-broken longitudinal sectional diagram of the striking tool 101. As shown in FIG. 7, in the striking tool 101, the rotation of a motor 102 housed within a motor casing 103 is transmitted to a crank shaft 114 by means of a pinion 106, a counter gear 117 and a final gear 118 within a gear cover 108, whereby the crank shaft 114 is driven and rotated. Then, the rotation movement of the crank shaft 114 is converted into the reciprocal linear movement of a piston 125 by a con rod 127. Thus, since the pressure of the air within an air chamber 126 defined by a piston 125 within a striker 124 changes due to the reciprocal operation of the piston 125, the striker 124 reciprocally moves within a cylinder casing 119 and so intermittently collides with an intermediate member 131. As a result, the striking force from the intermediate member 131 is transmitted to a tip end tool 132 which is fit within a tip end tool holding member 121 so as to be able to slide therein freely, whereby a required operation such as chipping, crushing of a scraped member such as concrete can be performed.
However, in such a kind of striking tool 101, since the tip end tool holding member 121 for holding the tip end tool 132 is rigidly coupled to the cylinder casing 119 by means of bolts 122, an impact force generated at the tip end tool holding member 121 is transmitted to the cylinder casing 119, the motor casing 103, the gear cover 108 etc. as it is. Thus, noise is generated from these members and further the damages of respective portions such as the breakage at a portion near the handle 110 are raised, whereby there arises a problem that the durable life time of the striking tool 101 is degraded.
In view of the aforesaid conventional technique, an impact force attenuation structure shown in FIGS. 8 and 9 is proposed (see JP-U-A-60-172681).
That is, FIG. 8 shows a longitudinal sectional view of the tip end portion of a striking tool and FIG. 9 is an enlarged diagram showing the details of a portion C in FIG. 8. In these figures, a reference numeral 220 depicts a cylinder housed within a cylinder casing 219, 224 a striker fit within the cylinder 220 so as to be able to slide therein freely, 231 an intermediate member, and 221a tip and tool holding member for holding the member 232.
The tip end tool holding member 221 is attached to the cylinder casing 219 in a manner that the flange portion 221a thereof is abutted against the front end surface of the cylinder casing 219 and the flange portion 221a is fastened to the cylinder casing 219 by passing bolts 222 therethrough and fastening the bolts. A buffer member 242 is sandwiched between the flange portion 221a and a plate 245 to constitute the impact force attenuation structure. To be concrete, as shown in FIG. 9, a collar 244 is passed through the tip end tool holding member 221 and the buffer member 242. Then, the plate 245 and the collar 244 are fastened to the cylinder casing 219 by the bolts 222 passing through the collar 244 and the plate 245, thereby constituting the impact force attenuation structure.
According to such an impact force attenuation structure, at the time of the collision to the tip end tool holding member 221 at the most advanced positions of the tip end tool 232 and the intermediate member 231, the tip end tool holding member 221 advances while pressing the buffer member 242, the impact force at the time of the collision is absorbed and buffered by the elastic deformation of the buffer member 242.